This application claims the priority of Patent Document 199 21 965.6, filed May 12, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a fine-toothed combing structure of an opening roller for an open-end spinning machine, comprising teeth whose spacing significantly exceeds the height of the teeth and which teeth have a positive front angle.
A fine-toothed combing structure is understood as one having a tooth height measuring less than 2 mm, and when, in comparison to the height of the teeth, there is a relatively large spacing. Such fine-toothed combing structure were originally developed in order to combine the positive features of both standard toothed combing structure and needle rollers (see Artzt/Egbers, Technology of Rotor Spinning, Melliand 1979). In practice, fine-toothed combing structure are primarily applied in the spinning of synthetic fiber material. Opened fibers from such material are relatively stiff and tend, at the entrance to the feeding channel, not to leave the teeth of the opening roller when they should. For this reason, extremely fine teeth have proven to be effective, as the fibers do not penetrate too deeply into the fine-toothed combing structure and therefore can be reliably further transported into the feeding channel. For opening the fibers from the fed fiber material, however, teeth having features counter to the ones mentioned above are more advantageous. For example, a relatively large front angle is purposeful for opening, while the same large front angle is counterproductive to releasing the single fibers at the entrance to the feeding channel. This disadvantage can be partly compensated for by increasing the speed of the opening roller, whereby there is then the risk that the single fibers will come into contact too often with the teeth, owing to the large number of same, thus leading to fiber damage.
It is an object of the present invention, in particular in the case of synthetic fiber materials having stiffer fibers, to find a suitable compromise in regard to the fine-toothed combing structure so that, on the one hand, the fiber material can be opened reliably, and on the other hand that the transported fibers can be released at the right time to the feeding channel. These advantageous features should also be effective in the eventuality of a speed increase of the opening roller.
This object has been achieved in accordance with the present invention in that the spacing of the teeth measures at least three times that of the height of the teeth and in that the front angle measures a maximum of 10xc2x0.
Because of the increased tooth spacing in relation to prior art, the number of teeth is reduced in such a way that the fibers do not receive any more knocks in the fine-toothed combing structure before they are released at the feeding channel than they would in a standard combing structure and at a slightly reduced speed of the opening roller. The front angle is of such a size that, on the one hand, it permits a reliable opening of the fiber material, and on the other hand is still small enough to permit the fibers a timely release from the fine-toothed combing structure.
In tests, dimensions, whereby the tooth spacing measures at least 4.5 mm, the front angle maximum 7.5 mm and the teeth height approximately 1.5 mm have proven to be a good compromise. If, in addition, the apex angle between the tooth front and the tooth back measures between 30xc2x0 and 40xc2x0, the tooth flanks are still large enough to transport the opened fibers from the opening zone to the entrance of the feeding channel.
In a particularly advantageous embodiment of the present invention, the flank angle between two tooth flanks measures between 8xc2x0 and 10xc2x0. It is hereby particularly favourable to make the tooth flanks symmetrical in relation to the tooth form. This is not possible with a standard wire combing structure. For this reason, a flank angle of this kind can only be realized whenxe2x80x94as is indeed knownxe2x80x94the teeth are ground from the solid material of the opening roller.
These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawings. following detailed description thereof when taken in conjunction with the accompanying drawings.